The present invention relates to a method for preparing an improved antiperspirant composition which can be incorporated into an antiperspirant formulation suitable for aerosol application.
Aerosol formulations under pressure have become popular as a convenient form for application of antiperspirant formulations to the skin. Aerosol antiperspirant and deodorant products now occupy a majority of the market for antiperspirant and deodorant products.
An aerosol product which possesses the attractive cosmetic properties and convenience benefits of currently available aerosol deodorant products and which additionally possesses substantial antiperspirant effects without excessive skin irritation would be highly desirable. Since the known inorganic astringent salts possess far greater antiperspirant activity than the organic astringent salts heretofore suggested for aerosol use, the inorganic salts must be used, despite the formulation problems involved, to provide such a product.
Among the most effective astringent inorganic salts are aluminum chloride and aluminum chlorhydrate. Aluminum chlorhydrate, also known as aluminum chlorhydroxide complex or basic aluminum chloride, has an approximate atomic ratio of aluminum to chlorine of 2:1, e.g., 2.1:1 to 1.9:1, and an empirical formula of Al.sub.2 (OH).sub.5 Cl, existing as a hydrate in solid form.
The efficacy of an antiperspirant composition is largely dependent upon the relative activity of the astringent salt employed therein. However, skin irritation results from the low pH of many conventional antiperspirant formulations. It is known that urea is very effective in reducing skin irritation caused by these formulations without reducing their efficacy. However, the large particle size and hygroscopicity of urea so far has prevented its incorporation into dry aerosol type antiperspirant products.
Accordingly, it is a primary object of this invention to provide a method for making an antiperspirant composition which can be effectively incorporated into an aerosol antiperspirant formulation.
It is a further object of this invention to provide a method of incorporating urea in a "dry" power aerosol antiperspirant formulation in which skin irritation and valve clogging are minimized.